SC11 Spectrum Analyser

The spectrum analyser displays the waveform and spectrum of the required channel. With the DAQCard-6024E this can be all 3 magnetic field axes and the auxiliary channel giving a full 4 channel capability as shown in the figure below.

This tool has a wide range of units for use with all the sensors. The software integrates the output of the accelerometer to provide measurements of velocity and displacement as well as acceleration.

Tracking cursors are provided to measure features of the selected spectrum as well as define bands for RMS measurement. Harmonic cursors, as in the figure below, can be used to recognise harmonics in the spectrum and enable more accurate measurement of the fundamental frequency.

The spectrum can be averaged to reduce noise. In conjunction with the Wilcoxon 731A accelerometer this enables state of the art measurements of vibration. The figure below shows a displacement spectrum measured on a concrete floor in a vibration free location during the night to further reduce any vibrations. This spectrum demonstrates the noise limit specification of the vibration sensor.

In a similar way to averaging, the peak values over a period of time can be displayed, for example to provide an estimate of the worst case vibrations at a site.

Below is a figure of a typical 1/3 octave analysis display. In version 4.2 the number of points has been increased from 2000 to 4000 allowing the 1/3 octave bands to go to a lower frequency than in previous versions. The total amplitude of the frequency components in each band is computed to provide the histogram display. The figure also shows an electron microscope specification that has been loaded in for comparison with the measurements. In this case the spectrum is magenta, showing that the specification has been exceeded. When more than one channel is displayed, the displayed specification relates to the selected channel only. Version 4.2 now allows a previously recorded spectrum to be imported as a specification, thereby allowing direct comparison with previous measurements.